1. Field of the Invention
This invention relates to an image processing apparatus and method as well as an image processing program.
2. Description of the Related Art
There are instances where color bleeding (a purple fringe) is visually recognized in an image obtained by imaging using a digital still camera or the like. If an edge having a large difference in luminance (luminance gradient) is present in a capture imaged owing imaging of a high-luminance subject (e.g., a light source), color bleeding readily occurs at the periphery of the image edge.
According to the specification of Japanese Patent Application Laid-Open No. 2009-268033, an area in which the signal level increases or decreases monotonically is discriminated as a color bleed area and a color bleed correction is applied in accordance with amount of change in color in areas other than the color bleed area. Since all areas in which the signal level increases or decreases monotonically are subjected to a color correction, erroneous corrections readily occur. In addition, since a color selected irrespective of the color of the object is corrected, there is a possibility that an unnatural color correction will result.
The specification of Japanese Patent Application Laid-Open No. 2006-135745 describes that purple fringing becomes less conspicuous by lowering saturation. The color of a purple fringe remains the purple color. Further, if saturation is reduced partially, color continuity becomes unnatural.
According to the specification of Japanese Patent Application Laid-Open No. 2002-262299, a region in which the detection value of an edge detection filter is greater than a prescribed value is adopted as a high-luminance region and Cr, Cb signals are averaged to thereby reduce false colors. In order to correct purple fringing occurring over a wide range, filter size must be enlarged, in which case there is the danger than erroneous determinations may be made.